Various ball games such as baseball, softball, tennis, volleyball, table tennis, soccer, squash and handball require practice at hitting, catching, retrieving, returning or other specific maneuvers to achieve proficiency in the game. Hence propelling the ball repeatedly with accuracy into a predetermined area of the air or along the playing surface is very desirable in the practice and the training of a participant. A machine is preferable for propulsion of the ball since the desired velocities, spins, curves, and accuracies cannot always be obtained by a person.
An excellent machine for throwing baseballs and tennis balls at constant velocity and with consistent accuracy is known as the "Fireball," a trademark of K-Lin Specialties Inc. of Manhattan Beach, California. It reflects the teaching of the previously mentioned Kahelin patent and application and is used during practice sessions by teams in professional leagues, schools, Little League, and by park and playground teams. It is light, mobile, easy to erect for use and easy to disassemble for transportation and storage. In the Fireball machine, balls are automatically fed down a chute into a propulsion chamber through a ball entrance opening or breech behind which is a chamber for supplying the compressed gas which propels the balls one at a time and at predetermined intervals out of a barrel. A sleeve automatically covers the breech before the ball is propelled to prevent the compressed gas from escaping from the opening. The machine also has a barrel attachment at its muzzle end for imparting a selected spin to the ball as it leaves the barrel to stabilize the ball or make its flight similar to the flight of balls thrown or struck during normal play of the game.
It must be realized that such a machine is a precision device and although relatively economical it is, of course, more expensive than the usual expedient of providing a highly trained player to produce the proper motion of the ball. It should also be realized that tennis and baseballs are approximately the same size so that a single barrel can be used to propel the balls without substantial modification. However, tennis and baseball are primarily summer sports and therefore there has been a need to adapt such a machine to other sports so that it can be used the year around thereby enabling additionaal utilization of the machine without substantially increasing the cost thereof. For example, handball, volleyball and squash which are played indoors, tend to be winter sports. In addition, softball and baseball are summer sports which are usually played in a school situation at different times during the day, that is, softball is played during normal school hours due to the reduced space required, whereas baseball is played after normal school hours when more space is available. Thus it can be seen that means to enable the propulsion of various sized balls can greatly enhance the value and usefulness of a basic Fireball machine.